Quick couplers are generally well known and can be found in many systems and devices. Typically, a quick coupler is fixed to an arm of a machine for connecting and disconnecting the arm to and from implements. For example, a quick coupler can be attached to the arm of an excavator for connecting and disconnecting the aim to and from implements such as buckets, hammers, rippers, and grapples. Such quick couplers are advantageous because they allow a machine operator to change quickly from one implement to another. Thus, the use of a quick coupler makes the machine more efficient and versatile.
Several different types of quick couplers have been employed in the past. One exemplary quick coupler is disclosed in U.S. Pat. No. 6,902,346 for a Hydraulic Coupler, filed on Mar. 15, 2002 and issued to Kenneth M. Steig, Jr., et al. on Jun. 7, 2005. Quick couplers, such as disclosed in Steig, typically include a body, recesses in the body for receiving machine pins of an implement, first and second locking latches for opening and closing the recesses, and a piston and cylinder device connected to the first and second locking latches for moving the latches between open and closed positions. In this type of quick coupler, the machine pins of the implement can be seated in the recesses and can be retained therein by the locking latches. However, a shortcoming to these quick couplers is that hydraulic failure can cause the piston to retract into the cylinder, thereby moving the locking latches from the closed position to the open position. This could cause the machine pins to unseat from the recesses and the implement to unexpectedly disconnect from the quick coupler. To prevent such disconnections, these known quick couplers can include a compression spring positioned around the piston to prevent the piston from retracting into the cylinder when hydraulic failure occurs. These quick couplers also provide manually installed locking pins for securing the first and second locking latches to the body of the coupler, thereby preventing the locking latches from moving to the open position upon hydraulic failure. The compression spring, however, is undesirable because it is susceptible to being overcome by forces acting on the piston, and the locking pins are undesirable because manual labor is required to install them.